Optical spectrometers are waveguide devices that use counter-propagating .chi..sup.2 nonlinear guide interaction to produce a required chromatic dispersion. In these devices, a reference guided mode interacts with a counter-propagating input infrared signal to generate a surface-emitting sum-frequency signal. The angle by which the up-converted visible signal is radiated is a function of the difference in the wavelength of the reference guided mode and the input signal. By fixing the reference wavelength, the frequency spectrum of the input signal is mapped to an angular spectrum of the up-converted signal in the far-field. The physical principle of the nonlinear parametric waveguide spectrometer is shown in FIGS. 3 and 4. The nonlinear guide acts as a grating in a conventional spectrometer. Two counter-propagating waves, one being a reference mode and the other an input signal, interact and generate surface-emitting sum-frequency signal radiating out of the top surface of the guide with an angle that is defined by the principle of momentum conservation. If one of the counter-propagating beams (reference beam) has a fixed wavelength, the frequency spectrum of the other counter-propagating beam (input signal) is mapped to the angular spectrum of the sum-frequency signal in the far-field. For example, see R. Normandin et al. "Monolithic, Surface-Emitting Semiconductor Visible Lasers and Spectrometers for WDM Fiber Communication Systems", IEEE Journal of Quantum Electronics, Vol. 27, No. 6, June 1991, pages 1520-1530, and D. Vakhshoori and W. Wang, "Integrable Semiconductor Optical Correlator Parametric Spectrometer for Communication Systems", Journal of Lightwave Technology, Vol. 9, No. 7, July 1991, pages 906-917.
A structure of a nonlinear guide which would be useful for generating green or blue light from radiation injected into the nonlinear guide was suggested by D. Vakhshoori et al. Conference on Lasers and Electro-Optics Technical Digest, Series 1991, (Optical Society of America, Washington, D. C.) Vol. 10, page 134, R. Normandin and R. L. Williams, Conference on Lasers and Electro-Optics Technical Digest Series 1991 (Optical Society of America, Washington, D. C.) Vol. 10, page 136, D. Vakhshoori et al., "Blue-Green Surface-Emitting Second Harmonic Generation of (111)B GaAs", Applied Physics Letters, Vol. 59, No. 8, 19 August 1991, pages 896-898, and D. Vakhshoori, "Analysis of Visible Surface-Emitting Second-Harmonic Generators", Journal of Applied Physics, Vol. 70, No. 10, 15 November 1991, pages 5205-5210. Such a structure would include a multilayer structure consisting of paired alternating compound semiconductor layers, each layer in a pair having different composition than the other layer in the pair. However, it is still desirable to provide the nonlinear parametric spectrometer with an imaging system which could map the near-field to far-field on compound semiconductor substrates.